Method of forming a surface finished workpiece for a vehicle from a metal sheet

ABSTRACT

In at least one embodiment of the present invention, a method of forming a surface finished workpiece for a vehicle from a metal sheet is provided. The workpiece is machined, which generates string chips having a desired maximum length for removal from the workpiece. The method comprises stamping the metal sheet into a blank having an edge with a contour, wherein the edge includes a plurality of interrupting segments spaced apart. Stamping the blank into the workpiece. Machining at least a portion of the workpiece to within a surface tolerance, wherein the edge is a stamping precursor of the portion, whereby the generated string chips break at interrupting segments such that the lengths are less than the desired maximum.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a method of forming a surface finished workpiece for a vehicle from a metal sheet which includes a machining operation that generates string chips.

2. Background Art

High volume automotive production methods for forming various workpieces for a vehicle, such as body panels, structural members, powertrain and transmission components including housings, have been modified over the years to improve efficiency and quality. Many of these components are made from formable metal sheets, which are typically tempered for stamping or other methods of forming. Low carbon steel, such as AISI 1008 and 1010, are commonly used because of their excellent formability and attractive cost.

However, some workpieces require a stringent surface tolerance that stamping may not directly provide and the additional step of machining may be necessary in order to meet these tolerances. Machining of low carbon steels or other highly formable metals may generate long stringy chips. These string chips may damage the finished workpiece surface, lead to increased production down time for chip removal or cause injury to workers.

In order to minimize these issues, a machining methodology generating shorter length string chips, which are more easily removed, is needed. One method is to reduce both the machining depth of cut and the feed rate. However, this method may result in lower production rates and, too often, insufficient length reduction of the string chips for efficient removal from the workpiece.

Accordingly, there exists a need for a production metal sheet forming methodology, which includes machining, whereby string chips may be generated below a desired maximum length.

SUMMARY OF THE INVENTION

In at least one embodiment of the present invention, a method of forming a surface finished workpiece for a vehicle from a metal sheet, wherein machining of the workpiece generates string chips having a desired maximum length for removal from the workpiece, is provided. The method comprises stamping the metal sheet into a blank having an edge with a contour, wherein the edge includes a plurality of interrupting segments spaced apart. The blank is stamped into the workpiece. At least a portion of the workpiece is machined to within a surface tolerance, wherein the edge is a stamping precursor of the portion, whereby the generated string chips break at the interrupting segments such that the lengths are less than the desired maximum.

In at least one embodiment of the present invention, a method of forming a surface finished workpiece for a vehicle from a metal sheet, wherein machining of the workpiece generates string chips having a desired maximum length for removal from the workpiece, is provided. The method comprises forming the metal sheet into a blank having an edge with a contour, wherein the edge includes a plurality of interrupting segments spaced apart. The blank is formed into the workpiece. At least a portion of the workpiece is machined to within a surface tolerance, wherein the edge is a forming precursor of the portion and the geometry of the interrupting segments are depressively reshaped during forming, whereby the generated string chips break at the reshaped segments such that the lengths are less than the desired maximum. The string chips are removed from the workpiece.

In at least one embodiment of the present invention a method of forming a surface finish workpiece for a vehicle from a metal sheet, wherein machining of the workpiece generates string chips having a desired maximum length for removal from the workpiece, is provided. The method comprises stamping the metal sheet into a blank having an edge with a substantially curved contour, wherein the edge includes a plurality of substantially flat segments spaced apart. The blank is stamped into the workpiece. A bladed structure is welded to the workpiece. At least a portion of the workpiece is machined to within a surface tolerance, wherein the edge is a stamping precursor of the portion and the flat segments are reshaped during stamping into a scalloped geometry, whereby the generated string chips break at the reshaped segments such that the lengths are less than the desired maximum. The string chips are removed from the workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a metal sheet die punching operation of one embodiment of a forming operation for a blank;

FIG. 2 is a plan view of one embodiment of a matched die and punch;

FIG. 3 is a plan view of one embodiment of a blank;

FIG. 3A is a enlarged plan view of one embodiment of an interrupting segment of a blank;

FIG. 4 is a sectional view of one embodiment of a forming operation for a workpiece;

FIG. 5 is a plan view of one embodiment of a workpiece in an unfinished form;

FIG. 6 is a sectional view of one embodiment of a workpiece in an unfinished form;

FIG. 7 is a sectional view of one embodiment of a workpiece in an unfinished form; and

FIG. 8 is a sectional view of one embodiment of a machine finishing operation of a workpiece.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Detailed embodiments of the present invention are disclosed herein. It is understood, however, that the disclosed embodiments are merely exemplary of the invention and may be embodied in various alternative forms. The figures are not necessarily to scale, some figures may be exaggerated or minimized to show the details of a particular component. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for the claims and/or as a representative basis for teaching one skilled in the art to practice the present invention.

Referring to FIG. 1, a sectional view of a metal sheet die punching operation of one embodiment of a forming operation for a blank is provided. A metal sheet 2 is interposed between a die 4 and a punch 6. In one embodiment, the metal sheet 2 is made of a highly formable metal alloy such as, for example, AISI 1008 or 1010 low carbon steel. Alternatively, the metal sheet may be an aluminum alloy such as, for example, an aluminum alloy from the AA5XXXX or AA6XXXX family.

The die 4 and the punch 6 are matched and move relative to one another between a closed position and an open position. In the closed position, the die 4 and the punch 6 shearingly interact with the metal sheet 2 to form a blank.

Referring to FIG. 2, a plan view of one embodiment of a matched die and punch is provided. The die 4 has an interior perimeter 10, and the punch 6 has an exterior perimeter 12. The interior perimeter 10 is matched and aligned with the exterior perimeter 12, such that the interior perimeter 10 forms a narrow gap between the exterior perimeter 12 when the die 4 and the punch 6 are in a closed position. The gap is such that the interposing metal sheet 2 is sheared between the perimeters 10 and 12, forming a matching blank.

The interior perimeter 10 of the die 4 includes positive segments 20 spaced apart. The exterior perimeter 12 of the punch 6 includes matching negative segments 22 to the positive segments 20. These matching segments 20 and 22 are aligned such that when the interior perimeter 10 shearingly interacts with the exterior perimeter 12, the resulting punched blank has corresponding segments along its edge.

Referring to FIG. 3, a plan view of one embodiment of a blank is provided. The blank 30 has an edge 32 with a contour. The edge 32 includes interrupting segments 34, which are spaced apart. FIG. 3A is an enlarged plan view of an interrupting segment 34 as depicted in FIG. 3. In one embodiment, the blank 30 may have a substantially circular contour with a diameter substantially between 10 and 20 inches. The edge 32 includes between 5 and 11 interrupting flat segments 34, substantially between 1.0 and 1.5 inches in length, which may be equally spaced apart. In an alternatively embodiment, the interrupting segments 34 may be depressions such as, for example, a slot. In yet another embodiment, the interrupting segments 34 may have a larger radius than a circular blank 30, or have a spline geometry that differs from the edge 32 contour.

Referring to FIG. 4, a sectional view of one embodiment of a forming operation for a workpiece is provided. Here, the blank 30 is formed into a workpiece by a stamping operation 40. For example, the stamping operation 40 may be a single stamping process or a progressive die stamping operation consisting of a series forming stations. Moreover, the blank 30 may be formed, for example, in any one of the initial series of steps in a progressive forming operation, which results in the workpiece.

The blank 30 is interposed between a cavity portion 42 and a core portion 44 of a matched tool die set. The blank 30 is forced into the cavity 46 by the core portion 44. The forcing of the blank 30 into the cavity 46 defines the geometry of the workpiece. The stamping operation reshapes the blank 30, including many of its features. For instance, the interrupting segments 34 may be reshaped by this forming operation. Alternatively, depending upon the desired geometry of the workpiece, the interrupting segments may substantially retain their original shape. For example, if a rectangular blank 30 with slotted or scalloped interrupting segments was stamped to form a 90 degree bend, the slotted or scalloped interrupting segments may substantially retain their original shape.

Referring to FIG. 5, a plan view of one embodiment of a workpiece in an unfinished form is provided. The workpiece 50 has an edge portion 52 including a plurality of interrupting segments 54, wherein the edge 32 of the blank 30 is the forming precursor of the edge portion 52.

Referring to FIG. 6, a sectional view of one embodiment of a workpiece in an unfinished form is provided. The workpiece 50 may have a shape suitable, for example, as a vehicle housing component. The edge portion 52 of the workpiece 50 may be somewhat rough or outside of a desired surface tolerance. In at least one embodiment, the interrupting segments 34 of the blank 30 have been reshaped into segments 54 of the workpiece 50. In one embodiment, the reshaped segments 54 have a scallop geometry. A stamping operation may also, for example, depressively reshape the interrupting segments 34 of the blank 30. The workpiece 50, as shown here, may include other design details, such as for example a hole 56.

Referring to FIG. 7, a sectional view of an embodiment of a workpiece 50 in an unfinished form is provided. Here, the workpiece 50 is shown with a substructure 60 welded 62 to the workpiece. The substructure 60 in one embodiment may be a bladed structure of an impeller housing for a torque converter assembly. Alternatively, the workpiece 50 may be a housing for a clutch plate assembly.

Referring to FIG. 8, a sectional view of one embodiment of a machine finishing operation 100 of a workpiece 50 is provided. The edge portion 52 is machined by a tool bit 102 to create a machined edge 104 to within a desired surface tolerance. The tool bit 102 may be any suitable device for machining known to those skilled in the art.

The material removed by machining the edge portion 52 generates string chips 106 having respective lengths. The interrupting segments 54 act as breaking points for the string chips 106, whereby the length of the string chips 106 are controlled to less than a desirable maximum length. By decreasing the spacing between the interrupting segments 54, the respective lengths of the string chips may also be decreased. In at least one embodiment, the desired maximum length of the string chips 106 is 2 inches. In at least one embodiment, machining the edge portion 52 includes a plurality of machining passes with the tool bit 102, whereby the interrupting segments 54 are completely removed.

The string chips 106 preferably are removed from the workpiece 50. Removing the string chips 106 helps to minimize damage and allow for efficient production of finished workpieces 50. In at least one embodiment, the workpiece 50 rests in a nest 108, which provides both support for the workpiece 50 while it is being machined and a flow path for removal the string chips 106.

While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims. 

1. A method of forming a surface finished workpiece for a vehicle from a metal sheet, wherein machining of the workpiece generates string chips having a desired maximum length for removal from the workpiece, the method comprising: stamping the metal sheet into a blank having an edge with a contour, wherein the edge includes a plurality of interrupting segments spaced apart; stamping the blank into the workpiece; and machining at least a portion of the workpiece to within a surface tolerance, wherein the edge is a stamping precursor of the portion, whereby the generated string chips break at the interrupting segments such that the lengths are less than the desired maximum.
 2. The method according to claim 1 further comprising removing the string chips from the workpiece.
 3. The method according to claim 1 wherein the geometry of the edge contour is substantially curved and the interrupting segments are substantially flat.
 4. The method according to claim 1 wherein the interrupting segments are equally spaced apart.
 5. The method according to claim 1 wherein the edge defines a substantially circular blank.
 6. The method according to claim 1 wherein the step of stamping the blank into the workpiece depressively reshapes the geometry of the interrupting segments.
 7. The method according to claim 6 wherein the reshaped segments have a scalloped geometry.
 8. The method according to claim 6 wherein the reshaped segments have a slotted geometry.
 9. The method according to claim 1 wherein the interrupting segments are depressions.
 10. The method according to claim 1 wherein the step of stamping the blank into the workpiece does not substantially reshape the interrupting segments.
 11. The method according to claim 10 wherein the interrupting segments have a slotted geometry.
 12. The method according to claim 10 wherein the interrupting segments have a scalloped geometry.
 13. The method according to claim 1 wherein decreasing the spacing between interrupting segments decreases the lengths of the string chips.
 14. The method according to claim 1 wherein the step of machining the workpiece includes a plurality of machining passes, which remove the interrupting segments.
 15. A method of forming a surface finished workpiece for a vehicle from a metal sheet, wherein machining of the workpiece generates string chips having a desired maximum length for removal from the workpiece, the method comprising: forming the metal sheet into a blank having an edge with a contour, wherein the edge includes a plurality of interrupting segments spaced apart; forming the blank into the workpiece; machining at least a portion of the workpiece to within a surface tolerance, wherein the edge is a forming precursor of the portion and the geometry of the interrupting segments are depressively reshaped during forming, whereby the generated string chips break at the reshaped segments such that the lengths are less than the desired maximum; and removing the string chips from the workpiece.
 16. The method of claim 15 wherein forming includes stamping.
 17. The method of claim 16 wherein the edge defines a substantially circular blank where the interrupting segments are substantially flat and the reshaped segments have a scalloped geometry.
 18. The method of claim 17 wherein the metal sheet is low carbon steel and the blank has a diameter substantially between 10 and 20 inches, wherein the edge includes between 5 and 11 interrupting segments substantially between 1.0 and 1.5 inches in length that are equally spaced apart, whereby the generated string chips have lengths that are less than 2.0 inches.
 19. The method of claim 15 wherein the step of machining the workpiece includes a plurality of machining passes, which remove the interrupting segments.
 20. A method of forming a surface finished workpiece for a vehicle from a metal sheet, wherein machining of the workpiece generates string chips having a desired maximum length for removal from the workpiece, the method comprising: stamping the metal sheet into a blank having an edge with a substantially curved contour, wherein the edge includes a plurality of substantially flat segments spaced apart; stamping the blank into the workpiece; welding a bladed structure to the workpiece; machining at least a portion of the workpiece to within a surface tolerance, wherein the edge is a stamping precursor of the portion and the flat segments are reshaped during stamping into a scalloped geometry, whereby the generated string chips break at the reshaped segments such that the lengths are less than the desired maximum; and removing the string chips from the workpiece. 